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Even at intermediate depths, where the environment is adequate for carbonate accumulations, a loss of calcareous microfossils may occur by the dissolution of CaCO3. Changes in the microfossil preservation indexes are a proxy for identifying oceanographic variations in the past. The goal of this study is to identify minor changes in the degree of preservation of foraminiferal assemblages in a supra-lysoclinal zone and their probable causes. Late Quaternary samples from three cores collected at intermediate water depths (1514, 1894 and 2091 m) on the Pelotas Basin continental slope were examined using the standard methodology for calcareous (foraminifera and coccolith) paleontological analyses. The age models were obtained based on AMS 14C dates and on the oxygen stable isotope (δ18O) record in foraminifera. Dissolution variations were identified using the coccolith-based CEX dissolution index, the carbonate content, foraminifera fragmentation index, the relationship between resistant and fragile planktonic foraminifera, and the abundance of fragile foraminifera Orbulina universa and Hoeglundina spp. Finally, the planktonic/benthic foraminifera ratio (P/B) was evaluated as a dissolution proxy, demonstrating non-applicability. Overall, the Marine Isotope Stages (MIS) 5 and MIS 1 (interglacials) show the best preservations, while MIS 4, 3 and 2 (glacials) show relatively poorer preservation. Although the cores were obtained well above the modern and the inferred glacial lysocline, periods of relative greater dissolution were identified which can be attributed to the advance of Upper Circumpolar Deep Water (UCDW). The best preservation indexes are attributed to the influence of North Atlantic Deep Water (NADW).

Calcified coccolithophores, a diverse and widely distributed group of marine microalgae, produce biogenic calcite in the form of coccoliths located on the cell surface. Using batch incubations of the coccolithophorid Pleurochrysis carterae, we investigated the responses of this calcification process to iron concentrations by changing the iron supply in the initial culture media from a normal concentration to 1 ppm (parts per million), 5 ppm, and 10 ppm. Time-dependent measurements of cell population, production of inorganic carbon (coccoliths), and organic carbon (organic cellular components) showed that elevated iron supply in the growth medium of P. carterae stimulates carbon sequestration by increasing growth along enhanced photosynthetic activity and calcification. In addition, the acquired time-dependent UV-Vis and FT-IR spectra revealed that iron fertilization-enhanced coccolith calcification is accompanied by a crystalline phase transition from calcite to aragonite or amorphous phase. Our results suggest that iron concentration has a significant influence on the marine carbon cycle of coccolithophores.

The dependence of skeletal alteration on time spent in the taphonomic active zone (TAZ) can generate a taphonomic clock, which can be used to quantify scales of time averaging and rates of skeletal production and recycling in the fossil record. However, the strength of the taphonomic clock is variable in present-day shallow marine environments and it is unclear how this strength varies with depth. Here, we assess the strength of the taphonomic clock in Nautilus macromphalus dead shells that were collected in cool-water, sediment-starved, epi- and mesobathyal environments off New Caledonia and range in postmortem age from few decades to several millennia. We find that, first, differences in the onset and extent of alteration states in the epibathyal zone ( 1,000 years). The onset of dissolution and formation of clay-goethitic coating occurs earlier (∼ 200 years) in the mesobathyal zone (> 750 m) than in the epibathyal zone. Clay-goethitic rims and boring infills show signs of microbial binding, pelletization, and coccolith dissolution and can represent nascent stages of glauconitization. Second, shells several centuries old show differences between right and left flanks (1) in the degree of encrustation and sponge bioerosion in the epibathyal zone and (2) in the extent of clay-goethitic coating in the mesobathyal zone. The upper flanks are ultimately removed in both depth zones, leaving relict half-shells that are millennia old. Third, the depth dependence of alteration can reflect a bathymetric decline in disintegration rates by heterotrophic borers due to a reduced productivity in the mesobathyal zone and an increase in dissolution rates due to the proximity of the aragonite compensation depth. The between-flank asymmetry in preservation implies (1) horizontal position of shells close to the sediment-water interface for several decades or centuries without being overturned or subjected to reworking and (2) shell exposure to two distinct taphonomic regimes separated by few centimeters, with the upper flank located in the TAZ and the lower flank facing a less aggressive sediment zone. The stable exposure of shells in the taphonomic active zone and slow alteration rates in bathyal environments allow discriminating between within-habitat time-averaged assemblages on one hand and environmentally or stratigraphically condensed assemblages on the other hand.

The article presents the results of pyrolysis (Rock-Eval) and pyrolysis–gas chromatography–mass spectrometry analysis of organic matter (OM) in the Holocene sediments of the Black Sea. The studied samples represent two parts of the sedimentary column: coccolith ooze with 2.8% Corg at the top and sapropels oozes with 8.5% Corg at the bottom. The deposition of Holocene sediments was inferred to take place under euxinic conditions, which are more favorable for organic-matter preservation and sapropel deposition during the Old Black Sea stage. The results show that the modern processes of microbially mediated methane oxidation in the Old Black Sea oozes are interpreted as the main cause of their apparently lower degree of diagenetic transformation as compared to that of coccolith oozes.

Calcareous nannofossils were observed to reconstruct the surface water conditions during late Pliocene climate transition (2.55 to 2.88 Ma) from the southern Gardar Drift, in the subpolar North Atlantic IODP Site U1314 (56°21.9’1N, 27°53.3’W). A total of 24 species from 14 genera were identified by polarizing microscope observation. The coccolith assemblages are dominated by species belonging to genus Reticulofenestra with different (size-defined) morphotype. Hence, changes in paleoceanographic condition are shown by the size variation of Reticulofenstraspecimens. Before ~2.76 Ma, the studied interval is characterized by the presence of an abundant larger Reticulofenstra group. It indicates warm oligotrophic and stable surface waters. At ~2.76 Ma the abundance of large Reticulofenstra decreased abruptly and alternated with small Reticulofenstra, suggesting collapse of sea surface stability with strong mixing condition. This event coeval with the final closure of the Central American Seaway (CAS) and the onset of intensified North Hemisphere Glaciation (NHG). Subsequently, the size variation of Reticulofenestra specimens exhibits a sequential pattern that is somewhere consistent with the interglacial-glacial cycle. The pattern begins with a gradual increase in size upward during interglacial suggesting warm oligotrophic and stable condition, and ends with an abrupt decrease in coccolith size during glacial suggesting eutrophic or strong mixing condition and destabilized sea surface waters.

A detailed study of the mineral composition and microstructure of the black shales associated with OAE1a (Eastern Russian Platform), OAE1b (Middle Caspian), and the host rocks has been carried out using X-ray diffraction, scanning electron microscopic, and microprobe analyses. The results provide important constraints for depositional environments in the sedimentary basins. Black shales with pyrite framboids imply euxinic (sulfidic) conditions with increased organic matter preservation. Disintegrating framboids suggest partial or complete dissolution of the organic matter inside the framboids due to increasing water oxygenation. OAE1a on the Eastern Russian Platform is heterogeneous as it includes thin interbeds of concretionary coccolith limestones within the interval of bituminous shales, and correlates with the Lower Aptian Rhagodiscus angustus nannofossil zone. The coccolith limestones indicate short intermittent episodes of interrupted stagnation, rapid oxygenation, and restoration of normal marine conditions. The presence of montmorillonite, albite, microcline, and diopside in the bituminous siltstones and in the host siltstones of OAE1a on the Eastern Russian Platform, as well as a high content of titanium in the black siltstones correlated with OAE1b in the Middle Caspian allow proposing significant input of pyroclastic material into the extant sea.

During biomineralization, organisms control the formation and morphology of a mineral using biomacromolecules. The biomacromolecules that most strongly interact with the growing crystals frequently get occluded within. Such an observation has been recently obtained for the calcium carbonate producing coccolithophore species Pleurochrysis carterae . Coccolithophores are unicellular algae that produce calcified scales built from complex-shaped calcite crystals, termed coccoliths. It is unclear how widespread the phenomenon of biomacromolecular occlusion within calcite crystals is in calcifying haptophytes such as coccolithophores. Here, the coccoliths of biological replicates of the bloom forming Emiliania huxleyi are compared with that of Pleurochrysis carterae , two species with different coccolith morphologies and crystal growth mechanisms. From high-resolution synchrotron X-ray diffraction, changes in the lattice parameters of coccolith calcite, after heating to 450 °C, are observed and associated with macrostrain originating from occluded biomacromolecules. We propose a mechanism governing the biomacromolecules’ interaction with the growing coccolith crystals and their likely origin.

Quantitative analyses of calcareous nannofossils were performed on 50 ditch-cuttings samples from a well drilled in the northern Campos Basin, Brazil. Nine zones and two subzones were recognised in the Paleogene-Neogene section. The absence of zones NN9-NN7 (earliest late-latest middle Miocene), NP25-NP21 (Oligocene) and NP18-NP1 (earliest late Eocene-Paleocene) implies the occurrence of three stratigraphic breaks/unconformities within the studied interval. Nannofossil assemblages present suggest an open-ocean depositional environment under oligotrophic-surface water conditions for the Miocene section of the well. Hughesius spp. and Umbilicosphaera spp., here named the “small dark” group, were recognised as an index of high nutrient concentration. We suggest that small coccolith/nannolith size is a better indicator of eutrophic condition than taxonomic affinity. Morphometric analysis of specimens of Sphenolithus belemnos and Sphenolithus disbelemnos showed that size tends to decrease within the highstand system tract. The influx of nutrients associated with the highstand could explain this size reduction and may also support our hypothesis that small specimens are indicative of high nutrient concentrations in the surface water.

Understanding past changes in sea surface temperatures (SSTs) is crucial; however, existing proxies for reconstructing past SSTs are hindered by unknown ancient seawater composition (foraminiferal Mg/Ca and δ18O), or reflect subsurface temperatures (TEX86) or have a limited applicable temperature range (Uk'37). We examine clumped isotope (Δ47) thermometry to fossil coccolith-rich material as an SST proxy, as clumped isotopes are independent of original seawater composition and applicable to a wide temperature range and coccolithophores are widespread and dissolution resistant. The Δ47-derived temperatures from 63 μm fraction removes most non-mixed layer components; however, the Δ47-derived temperatures display an unexpected slight decreasing trend with decreasing size fraction. This unexpected trend could partly arise because larger coccoliths (5-12 μm) are removed during the size fraction separation process. The c1 and

A study of coccolith assemblages from a box core from the central South Yellow Sea (SYS) was performed revealing fluctuations on their relative abundance (%) that can be related to climatic and hydrographic changes over the last 230 years (1780–2011). Total coccolith abundances ranged from 7.0 to 55.1×106 coccoliths·g-1 sediment. Although the abundance of different species varied widely throughout the core, seven taxa dominated the assemblage. Among these species, Gephyrocapsa oceanica was the most dominant species, and it showed an average percentage of 50.1%. The pattern of G. oceanica (eutrophic species) was opposite to that of the combined percentage of Braarudosphaera bigelowii and Umbilicosphaera sibogae (both oligotrophic species), indicating that in the Yellow Sea (YS), the distribution pattern of G. oceanica might be characteristic of nutrient availability. Similar patterns between G. oceanica and the Siberian High were observed on an inter-decadal time scale, indicating that the East Asian Winter Monsoon (EAWM) may be an important driver of ecological changes in the YS. When the EAWM prevails, both the Yellow Sea Coastal Current (YSCC) and Yellow Sea Warm Current (YSWC) strengthen, and the increasing nutrient availability and warmer water brought by the strengthened YSWC favor eutrophic and warm-water coccolithophore species, such as G. oceanica. This likely mechanism demonstrates that coccolith assemblages can be used as benign and reliable proxy for climate change and surface oceanography.

Satellite observations of middle to high latitudes show that modern ocean warming is accompanied by increased frequency and poleward expansion of coccolithophore blooms. However, the outcomes of such events and their causal processes are unclear. In this study, marine sediment cores are used to investigate past coccolithophore production north and south of the Subtropical Front. Calcareous pelagites from subtropical waters off northernmost New Zealand (site P71) and from subantarctic waters on Campbell Plateau (Ocean Drilling Program [ODP] site 1120C) record marked changes in pelagite deposition. At both locations, foraminiferal-rich sediments dominate glacial periods whereas coccolith-rich sediments characterise specific interglacial periods. Sediment grain size has been used to determine relative abundances of coccoliths and foraminifers. Results show coccoliths prevailed around certain Marine Isotope Stage (MIS) transitions, at MIS 7b/a and MIS 2/1 at P71, and at MIS 6/5e at ODP 1120C. Palaeo-environmental proxies suggest that coccolithophore production and deposition at P71 reflect enhanced nutrient availability associated with intense winter mixing in the subtropical Tasman Sea. An increased inflow of that warm, micronutrient-bearing subtropical water in concert with upper ocean thermal stratification in late spring/summer, led to peak phytoplankton production. At ODP 1120C during MIS 6/5e, an increased inflow of subtropical water, warm sea surface temperatures and a thermally stratified upper ocean also favoured coccolithophore production. These palaeo-environmental reconstructions together with model simulations suggest that (i) future subtropical coccolithophore production at P71 is unlikely to reach abundances recorded during MIS 7b/a but (ii) future subantarctic production is likely to dominate sedimentation over Campbell Plateau as modern conditions trend towards those prevalent during MIS 5e.

Here we present morphometrical evaluation, biogeographical distribution patterns and ecological information for five coccolithophore taxa (Calcidiscus leptoporus, C. leptoporus small, C. quadriperforatus, Umbilicosphaera foliosa and U. sibogae). This information is based on data obtained from surface sediments from the South Atlantic. The three Calcidiscus taxa can easily been distinguished by a combination of size and qualitative characters of their distal shields. Mostly encountered in the temperate to sub-polar regions C. leptoporus is the most abundant taxon and exhibits a negative correlation to temperature and salinity. Both, C. leptoporus small and C. quadriperforatus reach their maximum abundances also at higher latitudes and in the SW-African upwelling area. Their distributions therefore suggest preference for nutrient-enriched waters, which is also indicated by CCA. The two circular Umbilicosphaera species exhibit significant differences in coccolith morphology and show little overlap in size. Highest abundances are encountered in sub-tropical latitudes and are mainly derived from U. sibogae. In contrast, U. foliosa is present in very low abundances. Both species exhibit a preference for warm and oligotrophic conditions. However, U. foliosa increases in relative proportion to U. sibogae at the southernmost locations and in the Benguela upwelling. This could be interpreted as an affinity for slightly cooler and nutrient-enriched environments.

The early Aptian Oceanic Anoxic Event 1a (OAE 1a; ∼120 Ma) was caused by a global perturbation of the Early Cretaceous climate. It supposedly affected the composition of the marine biosphere, including the primary producers. This study aims at using the size evolution of three species of coccolithophores ( Biscutum constans , Zeugrhabdotus erectus and Watznaueria barnesiae ) for better understanding the impact of the OAE 1a on primary producers. A total of 30 samples derived from three sites, which cover the upper Barremian–lower Aptian interval, have been analyzed from the North Sea and the Lower Saxony Basin. The sections expose near-shore and shallow marine sediments. The measured data of B. constans and Z. erectus are characterized by a size decrease synchronous to the negative carbon isotope excursion. This size reduction marks the early phase of the OAE 1a, more precisely the carbon isotope segment C3. Coccolith sizes recover to pre-OAE 1a values in the aftermath of this brief interval. The short termed size reduction is seen as a reaction of specific nannofossil taxa to an increase in humidity during the early phase of OAE 1a. Due to high weathering rates and a substantial run-off, the amount of detrital material transported into the marine system increased significantly. Consequently light availability diminished in the surface waters, causing habitat changes for the photoautotrophic primary producers. Light-sensitive species like B. constans and Z. erectus adjusted by forming smaller skeletons, thereby reducing their size. This strategy allowed for dwelling in shallower water depth and thus compensated for the decrease in sun light. The sizes of W. barnesiae in contrast remain stable throughout the entire OAE 1a interval. W. barnesiae was not affected by these environmental shifts and is thus interpreted as being robust with respect to changes of the sun light.

The global warming debate has sparked an unprecedented interest in temperature effects on coccolithophores. The calcification response to temperature changes reported in the literature, however, is ambiguous. The two main sources of this ambiguity are putatively differences in experimental setup and strain specificity. In this study we therefore compare three strains isolated in the North Pacific under identical experimental conditions. Three strains of Emiliania huxleyi type A were grown under non-limiting nutrient and light conditions, at 10, 15, 20 and 25 °C. All three strains displayed similar growth rate versus temperature relationships, with an optimum at 20–25 °C. Elemental production (particulate inorganic carbon (PIC), particulate organic carbon (POC), total particulate nitrogen (TPN)), coccolith mass, coccolith size, and width of the tube element cycle were positively correlated with temperature over the sub-optimum to optimum temperature range. The correlation between PIC production and coccolith mass/size supports the notion that coccolith mass can be used as a proxy for PIC production in sediment samples. Increasing PIC production was significantly positively correlated with the percentage of incomplete coccoliths in one strain only. Generally, coccoliths were heavier when PIC production was higher. This shows that incompleteness of coccoliths is not due to time shortage at high PIC production. Sub-optimal growth temperatures lead to an increase in the percentage of malformed coccoliths in a strain-specific fashion. Since in total only six strains have been tested thus far, it is presently difficult to say whether sub-optimal temperature is an important factor causing malformations in the field. The most important parameter in biogeochemical terms, the PIC : POC ratio, shows a minimum at optimum growth temperature in all investigated strains. This clarifies the ambiguous picture featuring in the literature, i.e. discrepancies between PIC : POC–temperature relationships reported in different studies using different strains and different experimental setups. In summary, global warming might cause a decline in coccolithophore's PIC contribution to the rain ratio, as well as improved fitness in some genotypes due to fewer coccolith malformations.

Strains of the coccolithophore Emiliania huxleyi (Haptophyta) collected from the subarctic North Pacific and Arctic oceans in 2010 were established as clone cultures and have been maintained in the laboratory at 15 °C and 32 ‰ salinity. To study the physiological responses of coccolith formation to changes in temperature and salinity, growth experiments and morphometric investigations were performed on two strains, namely MR57N isolated from the northern Bering Sea and MR70N at the Chukchi Sea. This is the first report of a detailed morphometric and morphological investigation of Arctic Ocean coccolithophore strains. The specific growth rates at the logarithmic growth phases in both strains markedly increased as temperature was elevated from 5 to 20 °C, although coccolith productivity (estimated as the percentage of calcified cells) was similar at 10–20 % at all temperatures. On the other hand, the specific growth rate of MR70N was affected less by changes in salinity in the range 26–35 ‰, but the proportion of calcified cells decreased at high and low salinities. According to scanning electron microscopy (SEM) observations, coccolith morphotypes can be categorized into Type B/C on the basis of their biometrical parameters. The central area elements of coccoliths varied from thin lath type to well-calcified lath type when temperature was increased or salinity was decreased, and coccolith size decreased simultaneously. Coccolithophore cell size also decreased with increasing temperature, although the variation in cell size was slightly greater at the lower salinity level. This indicates that subarctic and arctic coccolithophore strains can survive in a wide range of seawater temperatures and at lower salinities with change in their morphology. Because all coccolith biometric parameters followed the scaling law, the decrease in coccolith size was caused simply by the reduced calcification. Taken together, our results suggest that calcification productivity may be used to predict future oceanic environmental conditions in the polar regions.

Using a coccolith weight analytic software (Particle Analyser), we analyze most abundant coccolith species in a sediment core from the central Western Pacific Warm Pool (WPWP) and calculate coccolith size and weight variations over the last 200 ka. These variations are compared with the trends of sea surface temperature (SST), primary productivity (PP), sea surface salinity (SSS), and insolation. Our results demonstrate that the size and weight of the coccoliths varied in response to variations of these factors, and their average total weight is primarily related to the relative abundance of the dominant species GEO (Gephyrocapsa oceanica). The variation in weight of EMI (Emiliania huxleyi) and GEE (Gephyrocapsa ericsonii) are mainly influenced by nutrients, and the variation of GEM (G. muellerae conformis) and GEO (G. oceanica) weight are mainly influenced by SST. For all of the taxa weight, PP and SST present apparent precession or semi-precession cycles, we consider that the mono-coccolith weight of the Equatorial Western Pacific is primarily affected by precession drived thermocline and nutricline variation.

Ongoing ocean warming and acidification are tied to the rapid accumulation of human-induced carbon dioxide (CO2) in the atmosphere and subsequent uptake of heat and CO2 by the surface ocean. These processes are expected to drive large changes in marine ecosystems. While numerous studies have examined the effects of ocean acidification on coccolithophores, less is known on their combined effect. In this study, we investigate temperature modulation of the carbonate chemistry sensitivity of the coccolithophore Emiliania huxleyi (RCC1827 from the Western Mediterranean) in a culture experiment. We analyzed the responses of coccolith morphology, particulate inorganic and organic carbon production, and sinking rate of individual cells. E. huxleyi was exposed to three CO2 levels (ca. 400 μatm, 900 μatm, and 1400 μatm) at 15°C and 20°C. Temperature adds to the negative effect of increasing pCO2 on coccolith morphology, suggesting that a significant number of E. huxleyi strains might suffer from a temperature increase, hampering their evolutionary success. Temperature amplified the positive effect of increasing pCO2 on organic carbon production, while modulating the response of calcification rates, indicating that the response to increasing pCO2 must be taken with caution depending on the temperature range studied. Sinking rates were positively correlated with temperature, whereas pCO2 did not have any effect. The combined effect of carbonate chemistry and temperature on the E. huxleyi ratio between particulate inorganic carbon and particulate organic carbon (PIC/POC) might also lower the sinking rate of aggregates. In conclusion, in a warmer and more acidified ocean, individual coccolithophore cells might sink faster, while aggregates might sink slower.

The Chatham Rise supports some of New Zealand's most economically valuable commercial fish stocks, fuelled by the highly productive waters of the Subtropical Frontal Zone (STFZ). Climate change-related shifts in phytoplankton community structure and function are predicted and may affect Chatham Rise productivity and deep-sea carbon sequestration by the biological carbon pump. However, little is known about how two major phytoplankton groups, diatoms and coccolithophores, will respond, since the seasonality of their productivity and export fluxes to the seafloor are not well known in the SW Pacific sector. This study is the first to report on the seasonal cycle of phytoplankton species fluxes in the STFZ, using a 12-month sediment trap record (1996–1997) on the northern (subtropical-influenced) and southern (subantarctic-influenced) flanks of the Chatham Rise. Diatom and coccolith flux assemblages were characterised and compared with biogeochemical fluxes from the same sites over the same time-frame. Northern phytoplankton flux composition was typical of the subtropics, with most particulate organic carbon (POC) and biogenic silica export associated with diatom fluxes. Fluxes to the northern trap were largely composed of coastal and benthic diatom taxa, reinforcing previous interpretations suggesting lateral advection and sediment resuspension along and across the Chatham Rise slope, influenced also by the Wairarapa Eddy. At the southern site, phytoplankton fluxes were on average an order of magnitude higher than at the northern site and comprised a combination of subantarctic and frontal zone diatom taxa. The majority of the annual diatom flux in the southern trap occurred during a spring Pseudo-nitzschia “pulse” associated with high biogenic silica and POC fluxes, which are inferred to be from subsurface chlorophyll maxima. High coccolith flux at the southern STFZ site was consistent with ecosystem processes observed from other subantarctic export regimes. Phytoplankton successions inferred from the sediment trap records suggest that coccolithophores precede diatoms in spring, which is contrary to expectations from classical studies where the opposite temporal trend is suggested. While maximum diatom species flux co-occurred with peak POC flux at both sites in spring, the estimated contribution of organic carbon associated with diatoms to POC flux was negligible (

The Austin Chalk Group is a very fine grained carbonate mudrock composed predominantly of microorganisms. To geologically characterize such a unit, the components and depositional and diagenetic features must be examined at the nano- to microscale, using micropetrography. Analytical methods include scanning electron microscopy, energy-dispersive X-ray spectroscopy, and thin-section analysis. Through micropetrographic analysis, we determined Austin Chalk composition to be mainly a matrix of coccoliths and coccolith elements in 20- to 30-micron peloids (probably marine snow). The most common larger components are planktic foraminifers and bottom-dwelling inoceramids. Austin Chalk mineralogy is predominantly calcite and siliciclastic components that are mainly clay minerals, quartz, and albite. Grain sizes of Austin Chalk components are generally in the clay- to medium-silt range. Four basic lithofacies define the Austin Chalk: (1) lithofacies 1: highly bioturbated, organic-matter-poor marly chalk, (2) lithofacies 2: highly bioturbated, moderately organic-matter-rich, marly chalk to chalky marl, (3) lithofacies 3: sparsely burrowed, poorly to moderately laminated, organic-matter-rich marly chalk, and (4) lithofacies 4: well-laminated, organic-matter-rich marly chalk to calcareous siliciclastic mudstone. These four lithofacies are distinguishable by their different fabrics, as well as by ranges in mineral composition and TOC content. Mean of organic-matter content ranges from 0.32 to 2.56 wt%, and the kerogen is generally Type I and Type II, except in lithofacies 1, in which Type III is more common. The abundance and type of organic matter suggest that the Austin Chalk can be self-sourcing. This investigation provides the basic nano- to micro-observations that will aid in other studies of the Austin Chalk Group and geologically similar formations relative to rock-strength/brittleness, source-rock potential, and reservoir quality.

The Lower Jurassic rock record contains abundant organic-rich mudrocks suitable for refining Early Jurassic time using Re Os organic-rich shale (ORS) geochronometry, such as those associated with the Sinemurian–Pliensbachian boundary event or the Toarcian Ocean Anoxic Event (T-OAE). Despite this, most studies to date have failed to obtain high precision, geologically meaningful, ages for such Lower Jurassic rocks. The cause of imprecision in Re Os ORS age dates, at least for the Toarcian, has been linked to subtle chemostratigraphic variations in 187Os/188Osi values. Here, we report the first high-precision Re Os ages of organic-rich shale packages of the Gordondale and basal Poker Chip Members of the Lower Jurassic Fernie Formation of Northwestern Alberta, Canada from the Western Canadian Sedimentary Basin (WCSB). Our Re Os age results bracket sediment deposition between the late Sinemurian-early Pliensbachian (192.11 ± 0.77 Ma [2σ] and 193.83 ± 1.34 Ma [2σ]) and late Toarcian (180.10 ± 2.68 Ma [2σ]). When coupled with chemo- (87Sr/86Sr and 187Os/188Os isotopes) and bio-stratigraphy (ammonite and coccolith), our Re Os ages correlate with regional and global stratigraphic tie points corresponding to pivotal points of Early Jurassic time, such as the Sinemurian–Pliensbachian boundary event, T-OAE, and late Toarcian, that are otherwise weakly constrained by isotopic methods. This integrative approach helps to place these events in a more robust temporal framework. Based on seawater Os isotope data, we also speculate that a previously unidentified positive Os isotope excursion exists at the Sinemurian–Pliensbachian boundary - perhaps triggered by late-stage Central Atlantic Magmatic Province (CAMP) volcanism.

Coccolithophores are one of the major groups of marine carbonate producers and are the most important pelagic unicellular calcifying organisms which play a pivotal role in the marine biogeochemical cycles. Since past few decades, coccolithophores have gained attention due to their unique role in the global carbon cycle and particularly due to their combined effects on the biological carbon and carbonate counter pumps. Owing to their high diversity, better preservation, fast turnover rate and significant role in the marine biogeochemical cycles, coccolithophores are identified as a potential proxy to reconstruct palaeoceanographic changes. In this review, a broad introduction of the biology and biogeography of extant coccolithophores is discussed with a brief overview on the preservation of the coccoliths and their applications. This includes how coccolith abundance, diversity and morphometric studies are used to reconstruct palaeotemperature, palaeosalinity, palaeoproductivity and palaeocirculation. In addition, implications of coccolithophores in the isotopic studies for the estimation of palaeotemperature and palaeoproductivity are also discussed.

Lower Oligocene coccolith limestones, known as Tylawa Limestones, in the Polish part of the Outer Carpathians have been analyzed using back-scattered electron (BSE) and charge contrast imaging (CCI) techniques and X-ray diffraction. The aim of the study was to reconstruct the fossilization history of the excellently preserved coccospheres, commonly observed in these sediments, deposited in the Paratethys basin. Multiple petrographic and geochemical analyses indicate that the exceptional preservation of coccospheres has been caused by the special coincidence of biostratinomic processes: pre- and post-depositional processes within the water&ndash, sediment interface and possible early cementation. We discuss the origin of the calcite and silica and provide some hypotheses regarding the environment and possible factors responsible for the spectacular preservation process. Based on the observed intermediate steps of calcite and silica alteration, we propose an extended model of biostratinomic processes and diagenesis. The possibility of finding exquisitely preserved coccospheres not only in soft clay-rich deposits but also in heavily lithified rocks extends the possibilities of research on the development and evolution of this group of organisms.

International audience; Body size is a major trait allowing the assessment of the respective control of evolution vs. (palaeo)environment on unicellular micro-organisms. Size patterns can be retraced for fossilisable micro-organisms, especially for coccolithophores, over geological time spans. Here, we present coccolith size patterns of Watznaueria barnesiae, which was a dominant and ubiquitous taxon in the Mesozoic. Measurements were conducted at two sites spanning the Upper Berriasian to Lower Hauterivian, namely the Vergol-La Charce section in the epicontinental Vocontian Basin, and the ODP Leg 185 Hole 1149B located in the Nadezhda Basin, in the Pacific Ocean. The obtained results were treated using multivariate analysis in order to detect significant trends of the measured parameters. Size values of coccoliths from both sites are remarkably similar and display comparable patterns, namely a statistically significant increase in the Lower Valanginian until maximum sizes recorded in the aftermath of the Weissert event (Upper Valanginian). Although W. barnesiae coccolith-size fluctuations, in the short term, might be related to environmental changes, the observed long-term size patterns are interpreted as the result of directional selection, in which a single phenotype is favored through time. Comparison with data available in the literature shows a return to a smaller size after the Turonian.

Coccolithophores are marine phytoplankton that are among the most prolific calcifiers widespread in Earth’s oceans, playing a crucial role in the carbon cycle and in the transport of organic matter to the deep sea. These organisms produce highly complex mineralized scales that are composed of hierarchical assemblies of nano-crystals of calcium carbonate in the form of calcite. Coccolith formation in vivo occurs within compartmentalized mineralisation vesicles derived from the Golgi body, which contain coccolith-associated polysaccharides (‘CAPs’) providing polymorph selection and mediating crystal growth kinetics, and oval organic mineralisation templates, also known as base plates, which promote heterogenous nucleation and further mechanical interlocking of calcite single crystals. Although the function of coccolith base plates in controlling crystal nucleation have been widely studied, their 3D spatial organization and the chemical functional groups present on the crystal nucleation sites, which are two crucial features impacting biomineralization, remain unsolved. Utilising cryo-electron tomography we show that base plates derived from an exemplary coccolithophore Pleurochrysis carterae (Pcar) in their native hydrated state have a complex 3-layered structure. We further demonstrate, for the first time, the edge and rim of the base plate – where the crystals nucleate – are rich in primary amine functionalities that provide binding targets for negatively charged complexes composed of synthetic macromolecules and Ca2+ ions. Our results indicate that electrostatic interactions between the negatively charged biogenic CAPs and the positively charged rim of the base plate are sufficient to mediate the transport of Ca2+ cations to the mineralization sites.

Significance Coccolithophores are abundant unicellular marine algae that produce calcified scales via a controlled intracellular process. Understanding the cellular controls over the calcification process is a pressing need to predict the influence of changing oceanic conditions on these major contributors to global marine calcification and carbon fluxes. Using several microalgae, and a combination of state-of-the-art cryoelectron and cryo soft X-ray microscopy, we demonstrate that the recently discovered calcium stores of coccolithophores are similar to the common calcium storage organelles of noncalcifying organisms. These results relate questions of environmental and evolutionary significance to a large body of physiological and molecular genetic findings of better-characterized organisms, and therefore provide fresh entry points for understanding calcification in coccolithophores., Calcium storage organelles are common to all eukaryotic organisms and play a pivotal role in calcium signaling and cellular calcium homeostasis. In most organelles, the intraorganellar calcium concentrations rarely exceed micromolar levels. Acidic organelles called acidocalcisomes, which concentrate calcium into dense phases together with polyphosphates, are an exception. These organelles have been identified in diverse organisms, but, to date, only in cells that do not form calcium biominerals. Recently, a compartment storing molar levels of calcium together with phosphorous was discovered in an intracellularly calcifying alga, the coccolithophore Emiliania huxleyi, raising a possible connection between calcium storage organelles and calcite biomineralization. Here we used cryoimaging and cryospectroscopy techniques to investigate the anatomy and chemical composition of calcium storage organelles in their native state and at nanometer-scale resolution. We show that the dense calcium phase inside the calcium storage compartment of the calcifying coccolithophore Pleurochrysis carterae and the calcium phase stored in acidocalcisomes of the noncalcifying alga Chlamydomonas reinhardtii have common features. Our observations suggest that this strategy for concentrating calcium is a widespread trait and has been adapted for coccolith formation. The link we describe between acidocalcisomal calcium storage and calcium storage in coccolithophores implies that our physiological and molecular genetic understanding of acidocalcisomes could have relevance to the calcium pathway underlying coccolithophore calcification, offering a fresh entry point for mechanistic investigations on the adaptability of this process to changing oceanic conditions.

A 19-year (1998–2016) continuous dataset of coccolithophore E. huxleyi distributions and activity in Arctic and Subarctic seas is presented. The dataset is based on optical remote sensing data (mostly OC CCI data) with assimilation of different relevant in-situ observations, preprocessed with authorial algorithms. Alongside with bloom locations, we also provide both detailed information on E. huxleyi impacts within the bloom area on marine environments and the subdatasets of quantified coccolith concentrations, particulate inorganic carbon content and CO2 partial pressure in water driven by coccolithophores. All data are presented on a regular 4×4 km grid at a temporal resolution of 8 days. The paper describes the theoretical and methodological basis for all processing and modeling steps. The data are available on Zenodo: https://doi.org/10.5281/zenodo.1402033.

Imprints of coccoliths can be expected on palynomorphs and phytoclasts in Rhaetian and younger palynofacies. They resemble the hollows left by spheroidal pyrite but may commonly be distinguished on the basis of shape and by occasional marks which reflect the arrangement of the calcite laths of which they were composed. Monospecific blooms are suggested when they are abundant and their size and form is more or less constant. Those which are larger than average and bear arcuate grooves subparallel to their margins may indicate the former presence of coccospheres. The occurrence of coccolith moulds in pre-Quaternary palynofacies both indicates marine influence on the environment of deposition and provides evidence for the affinity of amorphous organic matter in problematical preparations which are swamped with this material and contain few palynomorphs.

The Cretaceous ocean witnessed intervals of profound perturbations such as volcanic input of large amounts of CO2, anoxia, eutrophication and introduction of biologically relevant metals. Some of these extreme events were characterized by size reduction and/or morphological changes of a few calcareous nannofossil species. The correspondence between intervals of high trace metal concentrations and coccolith dwarfism suggests a negative effect of these elements on nannoplankton biocalcification processes in past oceans. In order to test this hypothesis, we explored the potential effect of a mixture of trace metals on growth and morphology of four living coccolithophore species, namely Emiliania huxleyi, Gephyrocapsa oceanica, Pleurochrysis carterae and Coccolithus pelagicus. The phylogenetic history of coccolithophores shows that the selected living species are linked to Mesozoic species showing dwarfism under excess metal concentrations. The trace metals tested were chosen to simulate the environmental stress identified in the geological record and upon known trace metal interactions with living coccolithophore algae.Our laboratory experiments demonstrated that elevated trace metal concentrations, similarly to the fossil record, affect coccolithophore algae size and/or weight. Smaller coccoliths were detected in E. huxleyi and C. pelagicus, while coccoliths of G. oceanica showed a decrease in size only at the highest trace metal concentrations. P. carterae coccolith size was unresponsive to changing trace metal concentrations. These differences among species allow discriminating the most- (P. carterae), intermediate- (E. huxleyi and G. oceanica) and least-tolerant (C. pelagicus) taxa. The fossil record and the experimental results converge on a selective response of coccolithophores to metal availability.These species-specific differences must be considered before morphological features of coccoliths are used to reconstruct paleo-chemical conditions.

As major calcifiers in the open ocean, coccolithophores play a key role in the marine carbon cycle. Because they may be sensitive to changing CO2 and ocean acidification, there is significant interest in quantifying past and present variations in their cellular calcification by quantifying the thickness of the coccoliths or calcite plates that cover their cells. Polarized light microscopy has emerged as a key tool for quantifying the thickness of these calcite plates, but the reproducibility and accuracy of such determinations has been limited by the absence of suitable calibration materials in the thickness range of coccoliths (0–4 µm). Here, we describe the fabrication of a calcite wedge with a constant slope over this thickness range, and the independent determination of calcite thickness along the wedge profile. We show how the calcite wedge provides more robust calibrations in the 0 to 1.55 µm range than previous approaches using rhabdoliths. We show the particular advantages of the calcite wedge approach for developing equations to relate thickness to the interference colors that arise in calcite in the thickness range between 1.55 and 4 µm. The calcite wedge approach can be applied to develop equations relevant to the particular light spectra and intensity of any polarized light microscope system and could significantly improve inter-laboratory data comparability.

The biotic response of calcareous nannoplankton to environmental and climatic changes during the Eocene–Oligocene transition was investigated at a high resolution at Ocean Drilling Program (ODP) Site 1263 (Walvis Ridge, southeast Atlantic Ocean) and compared with a lower-resolution benthic foraminiferal record. During this time interval, global climate, which had been warm under high levels of atmospheric CO2 (pCO2) during the Eocene, transitioned into the cooler climate of the Oligocene, at overall lower pCO2. At Site 1263, the absolute nannofossil abundance (coccoliths per gram of sediment; N g−1) and the mean coccolith size decreased distinctly after the E–O boundary (EOB; 33.89 Ma), mainly due to a sharp decline in abundance of large-sized Reticulofenestra and Dictyococcites, occurring within a time span of ~ 47 kyr. Carbonate dissolution did not vary much across the EOB; thus, the decrease in abundance and size of nannofossils may reflect an overall decrease in their export production, which could have led to variations in the food availability for benthic foraminifers. The benthic foraminiferal assemblage data are consistent with a global decline in abundance of rectilinear species with complex apertures in the latest Eocene (~ 34.5 Ma), potentially reflecting changes in the food source, i.e., phytoplankton. This was followed by a transient increased abundance of species indicative of seasonal delivery of food to the sea floor (Epistominella spp.; ~ 33.9–33.4 Ma), with a short peak in overall food delivery at the EOB (buliminid taxa; ~ 33.8 Ma). Increased abundance of Nuttallides umbonifera (at ~ 33.3 Ma) indicates the presence of more corrosive bottom waters and possibly the combined arrival of less food at the sea floor after the second step of cooling (Step 2). The most important changes in the calcareous nannofossil and benthic communities occurred ~ 120 kyr after the EOB. There was no major change in nannofossil abundance or assemblage composition at Site 1263 after Step 2 although benthic foraminifera indicate more corrosive bottom waters during this time. During the onset of latest-Eocene–earliest-Oligocene climate change, marine phytoplankton thus showed high sensitivity to fast-changing conditions as well as to a possibly enhanced, pulsed nutrient supply and to the crossing of a climatic threshold (e.g., pCO2 decline, high-latitude cooling and changes in ocean circulation).

Despite the oceanographic and geological significance of coccolithophores, the cellular mechanisms that underlie the intracellular production and subsequent secretion of their CaCO3 coccoliths remain poorly understood. Tools for labelling coccoliths and coccospheres in order to track their production would be of great value. We therefore evaluated the use of calcein, a derivative of fluorescein, as a method to fluorescently label coccoliths. The calcein method readily labelled pre-existing coccospheres in a range of coccolithophore species, including diploid and haploid life history phases, without compromising the coccolith structure. Calcite staining was verified though epifluorescence and confocal microscopy, and both stained and unstained cells and coccoliths were readily distinguished using flow cytometry. The fluorescence of stained coccoliths was retained for > 3 d allowing us to confirm the polar secretion of coccoliths by distinguishing pre-existing coccoliths from the accumulation and distribution of non-fluorescent coccoliths produced after calcein exposure. The calcein treatment had no significant effect on photosynthetic physiology, external calcite morphology, or growth rates of the cells over an 8 d period. The calcein staining method therefore represents a simple non-invasive, non-toxic optical technique to ‘tag’ calcium carbonate coccoliths and track their production in response to environmental manipulations or pharmacological treatments. Moreover, calcein staining of the coccosphere allowed for heterogenous patterns of calcification, growth, and cell division to be detected in a population of cells. This is the first description of the use of calcein to stain the biomineral structures of calcifying phytoplankton and this approach has the potential to be applied to detailed cytological investigations as well as high-throughput analysis of cultured cells or field populations.

International audience; Coccolithophore blooms occur regularly from April to June in the Bay of Biscay where they have been observed for many years from ocean-colour imagery thanks to the ability of their calcite plates to scatter light. They are easily depicted on interpolated images of non-algal Suspended Particulate Matter (SPM) derived from satellite reflectance data in May, at the time of the PELGAS (PELagique GAScogne) annual surveys. Over the springs 2012 to 2015, the PELGAS surveys provided in-situ data on the turbidity throughout the water column and on the hydrological environment prevailing during the blooms in the vicinity of the continental shelf break. The satellite-derived SPM in the area of coccolithophore blooms was closely related to measured turbidity in the euphotic zone. The deep maxima of coccolithophore-derived biomass were well observed in the turbidity signal throughout the water column. Despite the recurrence of SPM patterns due to coccolithophores in the well-mixed waters over the shelf break in spring, the variability of the satellite-derived SPM and the turbidity profiles was particularly high during the four years studied. The year 2013 showed persistent blooms from mid-April to the end of May over large areas inside and outside the shelf waters, whereas no bloom was observed in 2014, neither on SPM images nor through turbidity profiles. The presence or absence of coccolithophore blooms during the years 2012-2015 seem related to the level of stratification of the water column, with more intense blooms occurring during mixed conditions. These results should improve classification of the PELGAS surveys from those occurring in a coccolith-rich environment, synonymous with mixed and cold waters, to those occurring in a coccolith-poor environment where surface waters are warmer and more stratified.

Coccolithophores are globally abundant marine microalgae characterised by their ability to form calcite platelets (coccoliths). The coccoliths are produced internally in a Golgi-derived vesicle. Mature coccoliths are extruded from the cell to form a protective covering on the cell surface, known as the coccosphere. Current evidence indicates that calcite precipitation in the coccolith vesicle is modulated by coccolith-associated polysaccharides (CAPs). Whilst previous research into CAPs has focussed on their roles in calcite precipitation within the coccolith vesicle, little is known of their extracellular roles. Using fluorescent lectins, we visualise the extracellular polysaccharide-rich organic layer associated with external coccoliths and demonstrate that it differs between species in structure and composition. Biochemical analysis of polysaccharide extracted from coccoliths indicated substantial differences between species in monosaccharide composition and uronic acid content. In Coccolithus braarudii our studies indicate that polysaccharide-rich material is extruded with the coccoliths, where it plays a role in the adhesion of the coccoliths to the cell surface and contributes to the overall organisation of the coccosphere. Together, these results highlight the important extracellular roles of CAPs and their contribution to the dynamic nature of the coccosphere.

International audience; Coccolithophores have been extensively studied to understand the environmental control on calcification in a key biological group influencing the alkalinity of seawater. Previous studies have established that bulk calcification scales with cell division rates under a wide range of pH conditions. Yet, the fine scale ultrastructural changes of the coccoliths and therefore the pH-sensitive underlying mechanisms altering biomineralization of the coccoliths remain largely under-constrained. Using circularly polarized light and high-resolution microscopy, we have generated mass estimates of cultured Gephyrocapsa oceanica coccoliths grown in media with pH values ranging from 7.4 to 9.0. These mass estimates representing a bulk calcification response were related to the morphological changes within the coccoliths. From optimal (pH 8.6) down to pH 7.4 conditions, we have observed that impaired cell growth and lower calcite quota are accompanied by a 35% decrease in mean coccolith mass. The data further show that seawater acidification does not homogenously affect calcification of the coccoliths, as a clear decrease of the breadth of the tube (a structure surrounding the central area of the coccoliths) was detected, whereas all other ultrastructural components were far less impacted. We discuss this specific sensitivity to acidification as the possible consequence of the altered interaction of the acidic polysaccharides used for biomineralization and ambient concentration of protons released by calcification that substantially modify the growth patterns, the morphology, and ultimately the mass of the coccoliths.

Two new coccolith-agglutinated foraminiferal species, Pseudobolivina islandica n. sp. and Haplophragmoides atlanticus n. sp., are described from Recent and Upper Holocene sediments at Húnaflóaáll on the North Icelandic shelf. Specimens of the two species have been found only in the small (63–106 µm) fraction using the wet-counting method. This method allows preservation of these fragile tests, which are predominantly composed of coccoliths, mainly of the species Coccolithus pelagicus (Wallich, 1877).

Coccolithophores play a key role in the oceanic carbon cycle through the biological and carbonate pumps. Understanding controls on coccolithophore productivity is thus fundamental to quantify oceanic carbon cycling. We investigate changes in coccolithophore productivity over several Pleistocene glacial-interglacial cycles using a high-resolution coccolith Sr/Ca ratio record, which is an indicator of growth rate and thus a proxy for coccolithophore productivity. We use Middle Pleistocene sediments from the North Atlantic Integrated Ocean Drilling Program (IODP) Site U1313 (41.00′ N, 32.58’ W) spanning Marine Isotopic Stages 16 to 10 (638–356 kyr). The location of the record allows us to investigate processes affecting productivity in a mid-latitude setting and to unravel the effects of temperature and regional ocean circulation. Coccolithophore productivity shows a dominant glacial-interglacial cyclicity with higher productivity during glacials, which appears to reflect the southward migration of the North Atlantic high productivity zone currently located between 45° and 55° N. Spectral analysis of the productivity record reveals a suborbital variability consistent with forcing by insolation maxima superimposed on the front migration pattern. Similar to today, coccolithophore productivity during interglacials was enhanced when insolation was at its maximum in spring or in autumn, whereas during glacials, productivity was enhanced when summer/autumn insolation was at its maximum. We show that in the studied region, coccolithophore productivity was driven by processes reflecting regional insolation. Applying this information to model experiments is required to assess if coccolithophore productivity played a significant role in past changes of atmospheric CO2.

The most common biomineral produced in the contemporary ocean is calcium carbonate, including the polymorph calcite produced by coccolithophores. The surface waters of the ocean are supersaturated with respect to calcium carbonate. As a result, particulate inorganic carbon (PIC), such as calcite coccoliths, is not expected thermodynamically to dissolve in waters above the lysocline (~4500–6000 m). However, observations indicate that up to 60–80% of calcium carbonate is lost in the upper 500–1000 m of the ocean. This is hypothesized to occur in microenvironments with reduced saturation states, such as zooplankton guts. Using a new application of the highly precise 14C microdiffusion technique, we show that following a period of starvation, up to 38% of ingested calcite dissolves in copepod guts. After continued feeding, our data show the gut becomes increasingly buffered, which limits further dissolution; this has been termed the Tums hypothesis (after the drugstore remedy for stomach acid). As less calcite dissolves in the gut and is instead egested in fecal pellets, the fecal pellet sinking rates double, with corresponding increases in pellet density. Our results empirically demonstrate that zooplankton guts can facilitate calcite dissolution above the chemical lysocline, and that carbon export through fecal pellet production is variable, based on the feeding history of the copepod.

Sea spray aerosols (SSA) are amongst the largest contributors to global aerosol mass, with a profound effect on climate through their radiative and microphysical properties. The contribution of oceanic microbial activity to SSA properties is yet to be fully established. We assessed the SSA emission of the calcite units (coccoliths) that compose the exoskeletons of the cosmopolitan bloom-forming coccolithophore, Emiliania huxleyi. We show that while emission of airborne coccoliths occurs in steady-state conditions, it increases by an order of magnitude during E. huxleyi infection by its specific E. huxleyi virus (EhV). The seawater to airborne coccolith ratio during viral infection was 1:108, from which we can estimate ambient airborne coccolith concentrations as a function of oceanic bloom properties. The unique aerodynamic structure of the emitted coccoliths yields a characteristic settling velocity ~25 times smaller compared to sea salt particles of the same size, resulting in an enrichment of the coccolith fraction in the air. The predicted enrichment is established in lab results, which show that coccoliths are key contributors to coarse mode SSA surface area, comparable with sea salt aerosols. This study demonstrates the coupling between key oceanic microbial interactions and fundamental atmospheric processes like SSA formation and emission.

Marine algae are instrumental in carbon cycling and atmospheric carbon dioxide (CO2) regulation. One group, coccolithophores, uses carbon to photosynthesize and to calcify, covering their cells with chalk platelets (coccoliths). How ocean acidification influences coccolithophore calcification is strongly debated, and the effects of carbonate chemistry changes in the geological past are poorly understood. This paper relates degree of coccolith calcification to cellular calcification, and presents the first records of size-normalized coccolith thickness spanning the last 14 Myr from tropical oceans. Degree of calcification was highest in the low-pH, high-CO2 Miocene ocean, but decreased significantly between 6 and 4 Myr ago. Based on this and concurrent trends in a new alkenone ɛp record, we propose that decreasing CO2 partly drove the observed trend via reduced cellular bicarbonate allocation to calcification. This trend reversed in the late Pleistocene despite low CO2, suggesting an additional regulator of calcification such as alkalinity., The impact of future and past carbonate chemistry changes on calcifying plankton is poorly understood. Here, the authors show that coccolithophore degree of calcification decreased significantly between 6 and 4 million years ago, in line with declining aqueous CO2 concentrations.

Coccolithophores are important components of the phytoplankton community that play a unique role in the global ocean biogeochemical cycle though carbon fixation and calcium carbonate production. In addition, coccolithophores are good indicators of climate change as they have indicative organic and inorganic remnants in sediments. Emiliania huxleyi is the most typical representative of coccolithophores. Classification of coccolithophores is mainly based on coccoliths, which have very fine and complex structures and are easily destroyed during the sample collection process. It becomes a technical problem to identify coccolithophores. In this study, atomic force microscopy (AFM) was employed to observe coccoliths of Emiliania huxleyi with the purpose of establishing an AFM sample preparation method for coccolithophores. Centrifugation was found to be an appropriate method to deal with the AFM samples compared with filtration. An optimized protocol was established: cells are centrifuged at 3,000–4,000 rpm, 20°C, over 5 minutes, a precipitate is suspended in 0.05 M NH4HCO3 solution, and then a droplet of solution containing suspended coccoliths is pipetted onto a glass attached to the sample holder. High resolution images had been captured under the contact mode of AFM in air conditioning with a scan range of 50 μm and frequency of 1 Hz. The method is applicable to analyze the morphological features of coccoliths under various environ·方法· 848 生 物 多 样 性 Biodiversity Science 第 24 卷 mental parameters or gradients in the laboratory and is also suitable for coccolithophore bloom detection.

We investigated the calcareous nannofossils in the western Pacific and Bahama Bank of Caribbean Sea to reconstruct the paleoceanography and correlate with the global events. The absolute abundant of coccolith (number/g) are gradually increased from NN6 throughout NN19 Zone, while the relative abundance of Discoaster is decreased at Sites 782 in the western Pacific Ocean. The changes of the modal and maximum size of Reticulofenestra which are strongly reflected the collapse of sea surface stability, show four times in 8.8 Ma, 6.4 Ma, 5.4 Ma and 3.75 Ma at Site 782. On the basis of relationship between the changes of maximum sizes of Reticulofenestra and nutrient condition, these eutrophication events are clearly traceable to the western Pacific, Bahama Bank, northwestern Pacific Ocean and to the Indian Ocean. Two paleoceanographic events found in 8.8 Ma and 3.75 Ma are interpreted as change to high nutrient condition resulted in the intensification of Asian Monsoon and closure of Panama Isthmus.

Coccolithophore fluxes were determined at a mooring site off Cape Blanc (21° 08.79 N, 20° 41.29 W) from March 1989 to November 1991 to reveal inter-annual and seasonal changes in species composition. In total, 74 coccolithophore species were recorded, with Emiliania huxleyi, Florisphaera profunda and Gephyrocapsa spp. dominating the assemblage. Two major conditions were identified, leading to three different intervals with characteristic species composition and associated changing environmental factors: a ‘normal’ condition characterized by fluctuating fluxes with rather constant species assemblage and a ‘pulse-like event’ that reveals a significant increase in coccolithophore fluxes and change in species composition. From March 1988 to October/November 1990 and from May 1991 the coccolithophore assemblage was dominated by E. huxleyi, F. profunda, G. flabellatus, G. oceanic , and G. ericsonii . Variability within this assemblage points to the occurrence of different surface waters, such as offshore meandering filaments. In winter 1990/1991 a ‘pulse-like event’ followed that was characterized by a significant increase in coccolithophore fluxes and in the contribution of species of the genera Ophiaster, Acanthoica, Calciosolenia, Calciopappus and Syracosphaera . It is assumed that a fast settling took place after enhanced production occurred. The third interval from May to November 1991 displays reduced fluxes of all coccolithophore species. However, the species composition is similar to the first interval, thus seemingly the assemblage converges back to ‘normal’ conditions. Statistical analysis revealed small correlations of the tested environmental parameters, such as sea surface temperature, nutrient availability and lithogenic fluxes. Nevertheless a certain seasonality of the assemblages was obvious in terms of different correlation of these environmental factors. In autumn the variability of the coccolithophorid assemblage is correlated more to sea surface temperature, whereas the spring assemblage of coccolithophores is related more to nutrient availability. In contrast, the summer assemblage is, to some extent, influenced by all tested environmental factors, suggesting that further environmental parameters are more important. This may also explain that although the observed mean coccolith fluxes off Cape Blanc are well within the range of those in the SW African upwelling, as well as in more oligotrophic sites of the temperate North Atlantic and the Canary Islands, the assemblage composition is conspicuously different. The region off Cape Blanc stands out in terms of a lesser content of E. huxleyi but an enhanced proportion of a number of small-sized coccolithophore species.

International audience; Changes in Late Quaternary oceanic primary productivity in the western tropical Pacific were reconstructed using coccolith counts from the improved SYRACO system in piston core MD01-2386 retrieved from the Halmahera Sea near northwest New Guinea. The calculated primary productivity exhibits cycles on obliquity and precession timescales over the last 192 ka. There are marked differences between primary productivity records from the western tropical Pacific and the South China Sea (SCS), with the former being dominated by precession, and the latter showing all three Milankovitch cycles (eccentricity, obliquity and precession). Empirical Orthogonal Function (EOF) analyses reveal two significant EOF modes in the western tropical Pacific and SCS records. EOF-1 accounts for 38% of the total variance and exhibits obvious precessional cycles corresponding to Northern Hemisphere summer insolation, while EOF-2 accounts for 22% of the total variance and exhibits strong 41-kyr periodicity, suggesting different biological responses to hydroclimate changes in the two regions. A more complex hydroclimate regime influenced by the East Asian monsoon and the large contrast in regional topography and circulation during glacial cycles are considered to be the primary drivers of the stronger temporal variability in productivity in the SCS compared to the relatively stable western tropical Pacific. (C) 2015 Elsevier Ltd. All rights reserved.

Highlights: • Coagulation efficiency of the coccolithophorid Emiliania huxleyi was determined with Couette flow devices. • Higher coagulation efficiencies of cells were observed at lower growth rates. • Coagulation efficiency increases with the extracellular polysaccharides fraction. Abstract: Coagulation of small particles results in the formation of larger aggregates that play an important role in the biological pump, moving carbon and other elements from the surface to the deep ocean and seafloor. In this study, we estimated the efficiency of particle coagulation of the coccolithophore Emiliania huxleyi at different growth rates using Couette flow devices at a natural shear rate. To determine the impacts of chemical and biological factors involved in aggregate formation, we investigated how variance in organic matter composition, and in particular the presence of extracellular polysaccharides (EP), including transparent exopolymer particles (TEP) and acidic polysaccharides attached to the coccolith surface, affect the coagulation efficiency (α). When E. huxleyi was grown in a chemostat at different growth rates, coagulation efficiency increased from ~ 0.40 to 1 as cell growth rates declined and nutrients became more limited. With declining growth rate the concentration of EP and the number of detached coccoliths increased. Overall a close correlation between coagulation efficiency of E. huxleyi and the ratio of EP to total particle volume was observed. The minimum value of α of ~ 0.4 determined during this study is higher than estimates published for other phytoplankton cells, and may be related to the presence of EP attached to coccoliths. Based on our findings, we suggest that E. huxleyi is more prone to form aggregates, particularly during the decline of blooms, when increased production of EP and enhanced shedding of coccoliths coincide. This may be one explanation for why blooms of E. huxleyi play an important role in the biological carbon pump, efficiently enhancing the vertical flux of particles, as has been suggested by sediment trap studies.